1. Field of the Invention
This invention relates to a rotary valve for use in controlling the supply of hydraulic fluid to a hydraulically actuated reciprocating device such as a percussion drill or a pump and more particularly to a rotary valve for use in a hydraulic system including a reservoir and a hydraulically actuated piston wherein pressurized hydraulic fluid is supplied to opposite sides of the piston head.
2. Description of the Prior Art
Combined pumping and timing devices have been used to alternately supply hydraulic fluid to opposite sides of a piston head, but these devices are complex and cannot function continuously for any length of time due to severe maintenance problems. An example of such an arrangement may be seen in U.S. Pat. No. 3,654,961 entitled "Rotary Percussion Drill Having a Hydraulically Actuated Percussion Device," granted Apr. 11, 1972. The arrangement disclosed in the aforementioned patent may be used to provide impacting percussive forces to a drill steel by a hydraulic hammer in an apparatus for drilling bolt holes in a mine roof to accommodate roof bolts. The rotary valve of the invention described hereinafter may also be used with a hydraulically actuated percussion drill.